Essential oils are volatile oils derived from the leaves, stems, flowers or twigs of plants usually carrying the odor or flavor of the plant. Many essential oils are known to have antimicrobial activity.
For example, bisabolol, or more formally α-(−)-bisabolol (levomenol), is a natural monocyclic sesquiterpene alcohol. It is a colorless viscous oil that is the primary constituent of the essential oil from German chamomile (Matricaria recutita) and Myoporum crassifolium. It is almost insoluble in water and glycerin, but soluble in ethanol. The enantiomer, α-(+)-bisabolol, is also found naturally but is rare. Synthetic bisabolol (“Syn bisabolol”) is usually a racemic mixture of the two, α-(±)-bisabolol.
Another example is carvacrol, or cymophenol, C6H3CH3(OH)(C3H7), which is a monoterpenoid phenol. It has a characteristic odor of oregano. Carvacrol is present in the essential oil of Origanum vulgare (oregano), oil of thyme, oil obtained from pepperwort, and wild bergamot. The essential oil of Thyme subspecies contains between 5% and 75% of carvacrol, while Satureja (savory) subspecies have a content between 1% and 45%. Origanum majorana (marjoram) and Dittany of Crete are rich in carvacrol, 50% resp. 60-80%.
The antimicrobial activity of tested essential oils, measured as MIC (Minimum Inhibitory Concentration) is generally low, however, when compared to known antimicrobial agents such as Triclosan and cetyl pyridinium chloride. In many cases, the levels at which these compounds inhibit or kill microorganisms is high enough to present difficulties in formulation, odor, taste, cost and/or efficacy.
Therefore, there is a need for improved formulations comprising essential oils having antimicrobial properties.